In a 32-bit color system, each pixel is represented by 24-bit color (8 bits each per red/green/blue channel). The remaining 8 bits are the alpha (transparency) channel or unused. Please refer to the Wiki page for the information about True Color (24-bit): https://en.wikipedia.org/wiki/Color_depth.

The alpha channel, represented by the extra 8 bits in a 32-bit color space, provides information about the pixel's transparency or opacity. It determines how much of the underlying image or background shows through the pixel. Please refer to https://en.wikipedia.org/wiki/Alpha_compositing for more information.

 Therefore, a maximum of 16 million different colors (to be precise: 2²⁴ = 16 777 216 colors) is supported in both 32-bit and 24-bit systems.  The additional 8 bits of the alpha (transparency) channel in a 32-bit color system does not deliver any additional color information so there is no difference in terms of supported colors to a 24-bit color system. The technical document describing the connectivity and graphics remoting in Microsoft RDP protocol confirms that: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/00f1da4a-ee9c-421a-852f-c19f92343d73 (refer to the supportedColorDepths field description in ‘Client Core Data’ section)

In the context of a remote session, “32-bit color” (24-bit color plus transparency) only makes sense and provides benefits if a Windows-based application uses transparent elements, and the session only delivers separate windows of remote applications (without the whole remote desktop), which will be displayed on top of the local desktop (refer to Illustration #2 below)  For example, if the remote session uses Aero the title bar of the remote application window is semi-transparent. The transparency information from the alpha channel can be used to nicely blend the title bar (as well as other transparent parts of the remote application) with the underlying local thin client GUI elements.

In vSpace Pro software or native Windows Remote Desktop Connection Client, the session launched in desktop mode will not process the transparency information with the local desktop, even though the server side Windows OS host is configured to 32-bit color depth (refer to Illustration #1 below). This is because the blending of the transparent elements of the remote applications solely happens on the remote server. The thin client just gets ready to be displayed images of the remote desktop (including the images of the remote applications displayed on top of it). In this scenario, transparent elements from a remote application can only be seen inside the remote desktop session.

Following images illustrate the difference:

(Illustration #1) Remote session in desktop mode No benefit of using 32-bit color space as blending of remote applications with the local desktop is not possible.	(Illustration #2) Remote session in application mode The transparency information contained in the 32-bit color allows blending the transparent parts of remote application with local desktop

 

In summary, 32-bit and 24-bit color systems offer the user the same maximum of 16 million different colors (2²⁴ = 16 777 216 colors). The 32-bit color system adds 8-bit of transparency or opacity information and is only beneficial for a Windows-based application that leverages transparent elements and being delivered in a specific way in the remote session.

vSpace Pro supports 32-bit color depth (Windows OS host machine) for the following modern Windows OSes: